The broad, long term objective of this investigation is to study the effects of alcohol on prolactin secretion in lactating rats. Breast feeding is a natural, healthy and physiological function; unfortunately, many women are prevented from nursing or stop nursing earlier than planned because of difficulties with lactation. Alcohol consumption likely contributes to these nursing problems since more than 60% of American women drink alcohol. The effects of alcohol on lactation deserve attention because of alcohol's harmful effects on reproduction and growth. The major hormone controlling lactation is prolactin. Prolactin is essential for differentiation of the secretory and myoepithelial cells of the mammary gland during pregnancy, and to initiate and maintain lactation. Although several researchers have reported alcohol's effects on prolactin in humans and animals, its effects on prolactin secretion during lactation have not been examined fully. The specific aims of this proposal are to study the effects of alcohol administration on prolactin secretion, release mechanisms and central site(s) of action in catheterized, lactating rats. Rats will be given various doses of alcohol daily for 4 hours from days 5 to 12 of lactation. The blood alcohol will be maintained at a constant level by continuous infusion (comparable to having multiple drinks for several days). The effects of chronic alcohol exposure will be measured on: (1) suckling- induced release of prolactin; (2) concentrations of dopamine and serotonin and their metabolites, in select hypothalamic nuclei (these neurotransmitters have, either directly or indirectly, a major influence on prolactin release by the anterior pituitary); (3) serotonin-mediated prolactin release in lactating rats, and (4) prolactin release in response to thyrotropin releasing hormone (a well-characterized prolactin releasing factor acting at the pituitary level). Collectively, the results should provide significant information on alcohol effects on prolactin secretion during lactation, and its site and mechanism of action. These data will serve as important guidelines for future human studies dealing with alcohol abuse and its effect on lactational performance.